Impulse generator



Jan. 27, 1953 A. A. VARELA 2,627,030

IMPULSE GENERATOR Filed Aug. 3, 1945 ARTHUR AVARELA Patented Jan. 27, 1953 ()FFICE IMPULSE GENERATOR Arthur A. Varela, Washington, D. 0.

Application August 3, 1943, Serial No. 497,274

(Granted under Title 35, U. S. Code (1952),

sec. 266) 7 Claims.

This invention relates to intermittently operative oscillators for generating radio frequency pulses. Such pulse generators may be employed in radio echo ranging devices. For such use, and for other purposes, it is desirable that the operation of a pulse generator be stable under variation in load conditions.

It is accordingly an object of the invention to provide for stabilization of pulse length and pulse rate in a high frequency pulse generator. It is another object of the invention to provide a. pulse enerator operating under substantially constant grid bias during the pulse.

The invention will be further understood with reference to the drawing which discloses a circuit diagram of a pulse transmitter embodying the present invention.

The high frequency transmitter as shown in the drawing, may include four triodes comprising two push-pull pairs I and 2, 3 and 4, in parallel. Each pair is provided with a plate tank 5 and grid tank 6. These tanks constitute high frequency resonant line sections. The antenna I is fed by transmission line B inductively coupled to the plate tanks by loop 9. Plate potential is supplied by power transformer I0 and rectifier II which feed to the plate tanks through R. F. chokes I2. A storage capacitor [3 is connected between the output of rectifier I I and ground.

The filaments of the oscillator tubes are energized through lines I4 and are grounded through self-biasing resistors I5.

The pulsing characteristics of the transmitter are determined by the grid circuit components, now to be described. Grid tanks 6 are connected in parallel and returned to ground through resistor I6. In parallel therewith is condenser I1 and resistor I8.

The transmitter is normally held inoperative by bias developed across condenser I1 and grid resistor I6. Pulse generation is effected by the periodic establishment of a keying voltage across resistor I8 for decreasing the grid bias. This is accomplished by discharging an artificial line through the resistor.

The line comprises series inductances I9 and parallel capacitances 20, and is charged from a source of positive potential through isolating resistor 2 I. The means for switching the line across the resistor is vacuum tube 22, which preferably contains gas, but which may be a high vacuum tube.

The control element of tube 22 is keyed by a voltage supplied from a control source of desired frequency through transformer 23.

The pulse frequency is therefore that of the control source. The pulse length depends on the electrical length of the artificial line. For maintaining substantially constant bias on the transmitter during the pulse, resistor I 8 should be approximately the characteristic impedance of the line, so that discharge of the line produces a square voltage wave across the resistor. Condenser I! normally is of a large value so that the potential thereon varies only a limited amount by the flow of grid current during the pulse and the time constant thereof with resistor I6 is greater than the recurrence period.

The operation of the circuit is now apparent. Upon application of a positive keying alternation to the control element of tube 22, the line is discharged across resistor I8, decreasing the negative grid cathode bias on the transmitter and holding substantially this voltage thereon during the pulse. On completion of the discharge, the voltag developed across resistor I8 abruptly terminates and the transmitter is blocked. The tube 22, if gas filled, deionizes; and if a high vacuum tube, ceases conduction. Its control grid electrode receives cut-on bias on the negative alternation of the control frequency, and consequently the line is recharged through the isolating resistor 2|. Cycles recur successively as described.

It has been determined that by positively controlling the grid potential by the means described, pulse generation substantially independent of loading conditions can be effected.

Although I have shown and described certain and specific embodiments of the invention, I am fully aware of the many modifications possible thereof. This invention is not to be restricted except insofar as is necessitated by prior art and the spirit of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In a high frequency oscillator, means for controlling the grid bias comprising an impedance in the grid-cathode circuit, an artificial line, switch means for periodically connecting the line across said impedance for discharging the same and developing a bias control voltage in the grid cathode circuit.

2. A high frequency impulse generator including an oscillator, a resistance in the grid-cathode circuit thereof, and an artificial line, means for charging said line and switch means for periodically discharging said line through said resistance; said resistance being substantially'equal to the characteristic impedance of the line.

3. In a vacuum tube circuit, a grid-cathode circuit including an impedance, an artificial line, and switch means for periodically connecting the artificial line across the impedance-for controlling the grid-cathode bias.

4. In a high frequency impulse oscillator, means biasing the oscillator against oscillation, and means for periodically establishing an operating bias including an impedance, an artifi cial line, means for charging the line, and switch means for periodically discharging the line across the impedance.

5. Means for keying a high frequency impulse generator including an artificial line, means for charging the line, a resistance in a control circuit of the generator approximating the characteristic impedance of the line, an electron discharge tube connected between said line and said resistance, and control means for said tube operative periodically to render said tube conductive and to discharge the line through the re- .sistance.

6.'In combination, a high frequency oscillator 7 including an electron discharge device having a control grid, means normally applying a blocking bias on said control grid, an artificial line,

means charging said line, an impedance having a value substantially equal to the characteristic impedance of said line in the circuit of said control grid, and switch means periodically discharging said line through said impedance to periodically apply a substantially constant 1111- L 7. In combination, a high frequency oscillator, blocking means included in the control circuit 01' the oscillator normally biasing said oscillator against oscillations, an artificial line, means charging said line, an impedance having a value substantially equal to the characteristic impedance of said line connected in the control circuit of the oscillator, and switch means discharging said line through said impedance to apply a substantially constant unblocking bias in the control circuit so that said oscillator produces oscillations for a period of time determined by the electrical length of said line.

ARTHUR A. VARELA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 1 .Date

2,181,568 Kotowski Nov. 28, 1939 2,188,970 Wilson Feb. 6, 1940 2,221,666 Wilson Nov. 12, .1940 2,225,046 Hunter Dec. 17, 1940 2,255,839 Wilson Sept. 16, 1941 2,265,996 'Blumlein Dec. 16, 1941 2,266,154 Blumlein Dec. 16, 1941 2,3943'89 Lord Feb. 5 1946 2,405,069 Tonks July 30, 1946 2,405,552 Blumlein et a1. ,Aug. 13, 1946 2,406,871 Varela Se'ptQB, 1946 2,408,824 Varela Oc'tg8, 1946 2,417,834 Lord Mar. 25, 1947 FOREIGN PATENTS Number Country Date 479,935 Great Britain Feb. 19, 1938 

